The Archbishop of Canterbury and former oil executive Justin Welby has slammed the largest six energy companies for their "inexplicable" price hikes in the UK (Photo: Reuters)

The Archbishop of Canterbury Justin Welby has slammed the UK's largest six energy companies for their "inexplicable" price hikes and said they are under an obligation to behave "morally" instead of just maximising profits.

Following price hikes from SSE, British Gas and Centrica over the past week, Welby, a former oil executive, said energy firms should be aware of their social obligations.

"The impact on people, particularly on low incomes, is going to be really severe in this, and the companies have to justify fully what they are doing," said Welby.

"I do understand when people feel that this is inexplicable, and I can understand people being angry about it, because having spent years on a low income as a clergyman I know what it is like when your household budget is blown apart by a significant extra fuel bill and your anxiety levels become very high. That is the reality of it."

The 'Big Six' energy companies make up 99% of the UK energy sector.

Bills are due rise by an average of 9.2%, taking the typical annual dual fuel bill up by more than £120 to a record of £1,465.

The Markit Household Index indicator of British household confidence is currently held at 41, which is well below the 50 mark that indicates households are optimistic about their finances, following a fall in job security and frozen wages.

"[Fuel poverty] is a very severe issue... because real incomes are flat or declining and the cost of energy has gone up," said Welby.

"If we win that election in 2015 the next Labour government will freeze gas and electricity prices until the start of 2017. Your bills will not rise. It will benefit millions of families and millions of businesses," said Miliband in his conference speech.